This invention relates to check valves for backflow preventers.
Backflow preventers, examples of which can be found in U.S. Pat. Nos. 4,878,515, 4,044,787 and 3,918,477, are principally used for preventing contamination of a public water distribution system by preventing backflow or back-siphonage of contaminated water into the system. Usually, the backflow preventer assembly is installed in a pipeline between a main supply line and a service line that feeds an installation, e.g. hotels, factories or other institutions, or even a multi or single family residence. A backflow prevention assembly typically includes two check valves permitting flow only in the direction from the main supply line to the service line.